Water well sizing in Kenya

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Please help with considerations for sizing a water well in Kenya.

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3 Answers

  1. The FIRST consideration is the anticipated or required volume of water required.  The second is the available source(s) - volumes, depth, chemistry.  Everything after that is engineering and budgets.  You may use the values for water demand from the "AI" response posted.

  2. Answer from Open AI CHat GPT:

    1. Key Considerations for Water Well Sizing in Kenya

    ✅ Water Demand Estimation

    Step 1: Determine Daily Water Needs

    • Community Size: Estimate the number of people relying on the well.
    • Water Usage per Person: WHO recommends 20–50 liters per person per day .
    • Livestock & Agriculture: Account for cattle, goats, irrigation, etc.

    🔹 Example:

    • A village of 500 people using 30 liters/day each → 15,000 liters/day (15 m³/day)
    • Additional livestock & irrigation → Potential total: 30,000 liters/day (30 m³/day)

    ✅ Aquifer & Groundwater Availability

    • Hydrogeological Surveys: Conduct tests to locate reliable aquifers .
    • Static & Dynamic Water Levels: Measure seasonal fluctuations.
    • Recharge Rate: Ensure the well replenishes fast enough to meet demand.

    🔹 Typical Yield for Rural Kenya Wells:

    • Hand-pumped wells: 0.2–0.5 L/sec
    • Mechanized wells: 2–5 L/sec

    ✅ Well Depth & Casing Design

    • Typical Depth: 30–200 meters (depending on aquifer depth).
    • Casing & Lining:
      • PVC (for small wells)
      • Galvanized steel (for deep or high-yield wells)
      • Screened sections at the aquifer level to allow water entry.

    🔹 Important: Go deeper than the dry-season water table to prevent seasonal shortages.

    ✅ Pump Selection

    • Hand Pump (Afridev, India Mark II): Best for small communities (≤300 people) .
    • Solar-Powered Pump: Sustainable option for higher yields (≥1,000 people) .
    • Diesel or Electric Pumps: Needed for large-scale wells but require fuel & maintenance .

    🔹 Pump Capacity Example:

    • A 1 L/sec pump can provide 86,400 liters/day (~2,880 people at 30L/day) .

    ✅ Water Quality & Treatment

    • Test for: Bacteria (E. coli), fluoride, nitrates, iron, and arsenic.
    • Common Issues in Kenya:
      • Fluoride (>1.5 mg/L) – Found in Rift Valley, can cause dental/bone issues.
      • Salinity (coastal regions) – Requires desalination or filtration.

    🔹 Treatment Solutions:

    • Biosand Filters: Remove bacteria & turbidity.
    • Reverse Osmosis: Needed for high fluoride/salinity levels.

    2. Case Study: EWB Kenya Water Projects

    • Example: EWB-USA has worked in Turkana and Kisumu to build solar-powered boreholes .
    • Success Factors:
      • Community engagement: Train locals in well maintenance .
      • Hybrid solar/diesel pumping: Ensures reliable supply .
      • Water kiosks: Improve distribution efficiency .

    3. Recommended Steps for EWB Well Design in Kenya

    ✅ 1. Conduct a Hydrogeological Survey
    ✅ 2. Estimate Water Demand & Seasonal Variations
    ✅ 3. Choose an Appropriate Pump System (Hand vs. Solar vs. Diesel)
    ✅ 4. Design the Well Depth, Casing, and Lining for Long-Term Use
    ✅ 5. Implement Water Quality Testing & Treatment if Needed
    ✅ 6. Train the Community on Well Maintenance & Sustainability

    1 Comment

    1. This is a pretty good example of the limitations of "AI"!  Very general, inappropriate to Kenyan rural areas in many specifics, and nothing that can't be easily found with a general information search.  I hope nobody paid anything for it.

  3. Wells are normally sized based on their ability to accommodate the submersible pump since one will generally be required unless well is artesian. If you need a small 100mm diameter pump then your borehole should be finished at a minimum diameter of perhaps 120mm. If you are looking at higher flows where a 140mm diameter pump is expected to be required then the borehole should be finished at 150mm diameter… and so on… Geology / hydrogeology can also be a factor with sizing because these characteristics will help determine drilled diameters… ie you may require the borehole to be lined with screen and casing and surrounded with a formation stabiliser / filter pack and this would mean the drilled borehole will need to be at least 100mm larger diameter than the outside diameter of your screen which needs to be large enough ID to receive your expected pump. The main thing is don’t undersize it ! Good luck